Abstract: The soft clay stratum is prepared using the vacuum preloading method in a model test tank. Model tests on suction anchors with taut mooring system are conducted to study effects of different load directions on failure modes and the ultimate bearing capacities using the load-controlled method. The results show that the failure modes are still vertical pullout and the main factor affecting the ultimate bearing capacities is the reverse end-bearing resistance at the anchor tip although the lateral displacements and the ultimate bearing capacities obviously increase when the loading direction varies from 40 degree to 20 degree for the suction anchors with inclined loads at the optimal load attachment point. The ultimate bearing capacities associated with model tests are further predicted by the upper bound plasticity analysis and the limiting equilibrium analysis, which show that the predicted results do not reflect the effects of variations of loading direction on the ultimate bearing capacities if the reverse end-bearing resistance factor is taken as a constant. Therefore, a modified relation considering the effects of loading directions on the reverse end-bearing resistance is developed to correctly predict the ultimate bearing capacities.